This invention relates to a cooking utensil more particularly but not exclusively to cooking pans used in circumstances where foodstuffs are likely to adhere to one or more surfaces thereon.
There has been proposed in US4768427 in the name of the present Applicants, a process for providing an aluminium pan with a corrugated contact surface defined by concentric circular grooves. The surface is coated with a non-stick coating to provide a pan, which when used, has a reduced degree of adherence of foodstuffs as a consequence of the reduced area of contact of the corrugated surface, and during cleaning and/or removal of any foodstuff that has so adhered, contact between any cleaning tool or device is concentrated at the peaks of the corrugated surface with the troughs or valleys being left relatively unscathed so that any non-stick surface thereon is substantially preserved.
As aluminium is a relatively soft metal, forming the corrugated surface may be readily effected by machining the surface of the pan prior to a hardening (anodizing) process. However, for pans made of other materials, for example steel, such as disclosed in GB-A-1153823, which are of substantially increased hardness, machining of the corrugations is not a practical manufacturing technique. It is an object of the invention to provide cooking apparatus, and a method of producing same which is more applicable for use with pans made of harder materials.
According to the invention, there is provided a cooking utensil as claimed in claim 1.
Preferably, the corrugated surface is formed by forging or pressing.
Preferably, the substrate is roughened by grit blasting and the non-stick layer, preferably a PTFE multi-layer coating, is applied to the grit blasted, arc-sprayed surface.
A pan formed in accordance with the invention has a corrugated surface giving the advantages of the pan of US4768427, with the additional benefits of formation from a relatively hard material such as stainless steel and improved non-stick layer wearability, due to the combined anchoring effect of grit blasting and arc-spraying the substrate.
According to the invention in a second aspect, there is provided a method of forming a cooking surface on a cooking utensil as claimed in claim 7.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:
With reference to the figures, an embodiment of the invention is shown which is a kitchen utensil in the form of a frying pan.
The frying pan is provided with a heat receiving substrate 100 comprised of a heat receiving stainless steel layer 105, a cooking surface substrate 110 both formed from stainless steel of standard composition (ie Chromium 18%, Nickel 5%, Manganese 8.5% and the remainder Carbon Steel), which together sandwich an aluminium layer 115.
The substrate 110 is provided with a pattern of corrugations 200 (see Figure 1) forming square depressions of depth 0.30mm side length 2.85mm formed between ridges of width 1.65mm. The corrugations are formed in the substrate 110 by application of a circular die on the base of the pan under pressure, eg in a stamping press optionally under the influence of heat.
In order to provide adhesion for a non-stick coating, the substrate 110 is then grit-blasted to form a grit blasted surface 111, and then the substrate is arc-sprayed with a stainless steel alloy wire of the same composition as the pan substrate 110 to form a particulate arc sprayed layer 112.
The grit-blasting creates an initial rough surface 111 with the arc-spraying then creating a further, rougher surface with greater surface area for good adhesion of the non-stick coating. The arc-sprayed substrate also improves the coating's abrasion resistance.
The non-stick coating is sprayed onto the treated substrate in three layers, a primer coat, PTFE intermediate coat and PTFE top coat 125, 130, 135 in a manner known per se.